The present invention is directed to a diagnostic tool and more specifically to a diagnostic tool for communicating with a motor vehicle that includes multiple control units that implement at least two different communication protocols.
Today, motor vehicles include various electronic control units mounted in the motor vehicle. The control units may control various systems and/or subsystems within the motor vehicle. For example, a control unit may control an engine, a transmission, a brake or a steering mechanism. These control units are typically coupled to a variety of sensors and/or actuators. Depending on the vehicle, the control units within a motor vehicle may implement various different communication protocols. In addition, many of these control units may operate at different voltage levels and may transmit in differential or single-ended modes.
In a typical motor vehicle, an engine control unit receives a plurality of input signals. These input signals may include, for example, a coolant temperature sensor, an oxygen sensor, an intake manifold pressure sensor, an air-conditioner switch, a vehicle speed sensor, an accelerator switch, a throttle position sensor, a neutral switch and an engine speed sensor. The engine control unit receives and processes the input signals received from the various sensors and switches. In response to these input signals, the engine control unit may output various control signals. These control signals may control, for example, a canister purge solenoid, an exhaust gas recirculation (EGR) system actuator, an idling control actuator, an ignition coil and/or a plurality of fuel injectors.
A typical transmission control unit also receives a plurality of input signals from various sensors. In response to these input signals, the transmission control unit outputs various control signals. These control signals may control various automatic transmission actuators and thereby control an automatic transmission. In a typical motor vehicle, a brake control unit receives a plurality of input signals from a brake switch and/or a plurality of wheel speed sensors. In response to these input signals, the brake control unit may produce various control signals that control brake actuators of an anti-lock braking system.
A typical speed control unit receives input signals from a speed set switch and a vehicle speed sensor. In response to these input signals, the speed control unit adjusts a throttle actuator to run the motor vehicle at an approximately constant speed. The speed control unit may also receive input signals from a brake switch, an accelerator switch, a neutral switch, a deceleration switch and/or a resume switch. In response, the speed control unit may discontinue constant speed control or reset a constant speed after changing the speed of the motor vehicle. Thus, as described above, a typical motor vehicle utilizes multiple control units for controlling the operation of the motor vehicle.
One of the more important functions performed by a motor vehicle control unit involves the monitoring of motor vehicle emissions. The Federal Clean Air Act of 1990 required that all cars and light trucks sold in the United States after Jan. 1, 1996, adhere to the California Air Resources Board (CARB) requirements. A primary objective of the CARB requirements was the implementation of a system, within a motor vehicle, to monitor the electronic engine management and emission control systems of the motor vehicle. This system was to alert a driver, in the early stages, of an emission control component or system failure and provide diagnostic information about the failure. In response to the CARB requirements, on-board diagnostics (OBD) II was implemented. The Society of Automotive Engineers (SAE) has set forth numerous standards that are applicable to OBD II equipped motor vehicles. For example, SAE J2012 sets forth the common diagnostic trouble codes (DTCs) and SAE J2190 defines the common diagnostic test modes (DTMs).
An OBD II compliant vehicle can include one or more of three communication protocols; SAE J1850 variable pulse width modulation (VPWM), SAE J1850 pulse width modulation (PWM) and ISO 9141. Most current General Motors (GM) cars and light trucks implement the J1850 VPWM communication protocol. A majority of current Chrysler, European and Asian Import vehicles implement the ISO 9141 communication protocol. Most current Ford vehicles implement the J1850 PWM communication protocol. However, motor vehicles that are not OBD II compliant have implemented various other communication protocols. In addition, OBD II compliant motor vehicles may include motor vehicle control units that implement other non-OBD II compliant communication protocols.
In a typical motor vehicle when a fault occurs, that is monitored by a control unit, that fault is logged within memory. In a typical situation, a malfunction indicator light (MIL) is also lit to inform a driver of the motor vehicle that a problem exists. In attempting to trouble-shoot an indicated fault, a service technician typically connects a diagnostic tool to a diagnostic connector provided on the motor vehicle. A typical diagnostic tool includes a microcontroller and interface circuitry to convert the electronic signals supplied by a control unit in the motor vehicle to a signal that is readily useable by the microcontroller of the diagnostic tool.
Certain diagnostic tools have included multiple hard-wired communication circuits that allowed the diagnostic tool to interpret multiple protocols from different control units. Other diagnostic tools have included a field programmable gate array (FPGA). The FPGA allowed a diagnostic technician to download different images into the FPGA, such that the FPGA could accommodate different communication protocols. In this case, the FPGA served as a communication interface between one of the motor vehicle control units and the microcontroller located in the diagnostic tool. However, diagnostic tools including FPGAs of this nature have only provided one communication protocol interface at a time. That is, these FPGAs have required reprogramming (i.e., a new image was loaded into the FPGA) in order to communicate with a control unit that used a different communication protocol. However, many motor vehicles include multiple control units that implement different communication protocols within the same motor vehicle.
An embodiment of the present invention is directed to a diagnostic tool for communicating with a plurality of motor vehicle control units that implement at least two different communication protocols. The diagnostic tool includes a processor and a field programmable gate array. The processor executes diagnostic routines and thereby provides messages to one of the plurality of motor vehicle control units. The field programmable gate array provides a selectable multiple protocol interface that is coupled between the plurality of motor vehicle control units and the processor. The selectable multiple protocol interface converts processor messages into motor vehicle control unit readable formats and converts received control unit information into a processor readable format.
These and other features, advantages and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims and appended drawings.